This invention relates generally to vehicle brake control systems for limiting the spinning of power driven vehicle wheels during actual or attempted vehicle acceleration, and for limiting the skidding of vehicle wheels to which brakes are applicable during actual or attempted vehicle deceleration, and various component elements of such systems.
Several systems for controlling vehicle brakes to inhibit locking or skidding of the wheels are known in the prior art. For example, see U.S. Pat. No. 2,068,370 issued to R. J. Bush on Jan. 19, 1937 and entitled "Inertia Operated Control Device", which discloses the use of a rotating flywheel to inertially control the operation of the fluid valve, which valve, in turn, controls the maximum rate of deceleration of the vehicle wheel during the application of brakes thereto. U.S. Pat. No. 3,752,268 issued to Hans Gfeller on Aug. 14, 1973 and entitled "Braking System" also discloses a flywheel to perform the same function using a different structural combination.
One difficulty encountered with these prior art systems, as illustrated by the previously cited reference patents, is that they provide means for unloading vehicle brakes at a preselected and fixed maximum rate, independent of and without regard to the actual rate of deceleration of the vehicle as a whole, whether the rate of vehicle deceleration be relatively great as when braking on dry pavement, or whether relatively small as when braking on solid ice. Because such systems are preset against an aribtrary standard or reference, they cannot thereafter differentiate between widely varying road conditions which cause widely varying rates of deceleration of a vehicle when braking is applied. Moreover, such prior art systems do not use the actual speed of the vehicle as a reference against which to compare the speed of each wheel to which brakes are applicable to determine when an acceptable wheel skid condition is being exceeded. Rather, such prior art systems compare the speed of the brakeable vehicle wheels to an arbitrary reference rate of decleration, not the actual vehicle deceleration rate.
Another disadvantage of the prior art brake control systems for inhibiting wheel skid conditions, is that they operate the unloading of the brakes on an interruptable and discontinuous basis wherein no anti-skid protection is afforded until the system responds to a preselected, idealized set of initial conditions, at which time a valve or switch is suddenly actuated to unload the vehicle brakes. There is no provision made for continuous unloading of the vehicle brakes at a rate dependent upon the difference in speed between the brakeable vehicle wheels and the vehicle as a whole, so as to limit the onset of a skid condition in a smooth and continuous manner.
Moreover, the prior art systems do not employ inertial means, such as a rotating flywheel to continuously measure the instantaneous speed of the vehicle while decelerating. Also, such prior art systems do not provide means for preventing the spinning or slipping of power driven vehicle wheels under conditions of rapid acceleration or attempted acceleration, as on ice, for example.
Those anti-skid systems of the prior art which utilize electrical and electronic circuitry have the additional disadvantage of being difficult and critical to adjust and of being susceptible to radio interference in some cases. Another difficulty encountered in the brake control systems of the prior art is that means for obtaining vehicle braking is lost upon failure of such systems for any reason.
My invention substantially overcomes these and other difficulties inherent in brake control systems of the prior art.